Epitaxial growth of GaN films on lattice-matched ScAlMgO4 substrates

Abstract

High-quality GaN films have been epitaxially grown on ScAlMgO₄ (SCAM) (0001) substrates with an in-plane epitaxial relationship of GaN[1−100]//SCAM[1−100] by pulsed laser deposition (PLD). The effect of laser repetition rate on the qualities of GaN epitaxial films is studied in depth. It is found that as the laser repetition rate increases from 10 to 40 Hz, the qualities of as-grown ∼300 nm-thick GaN epitaxial films increase first and then decrease, and show the optimized values at a laser repetition rate of 30 Hz. The ∼300 nm-thick GaN epitaxial films grown with the laser repetition rate of 30 Hz present very high crystalline quality with full-width at half-maximum values for GaN(0002) and GaN(10−12) X-ray rocking curves of 0.18° and 0.40°, and reveal a very smooth surface with a root-mean-square surface roughness of 1.5 nm. The as-grown GaN films also show an in-plane tensile stress of 0.51 GPa. Meanwhile, cross-sectional transmission electron microscopy confirms the presence of sharp and abrupt GaN/SCAM hetero-interfaces.